1. Field of Invention
The invention relates to a fan, and, in particular, to a passive fan.
2. Related Art
As electronic products are rapidly developed to have high performance, high frequency, high speed and thinned size, the temperature of the electronic products is getting higher and higher. Thus, the unstable phenomenon occurs and thus influences the reliability and the lifetime of the product. Accordingly, heat dissipating has become one of the important issues in the electronic product, and a fan is frequently used in a heat dissipating device.
Referring to FIG. 1, a conventional fan 1 includes an impeller 11, a motor 12 and a frame 13. The impeller 11 has a plurality of blades 111. The motor 12 is disposed at a center of the impeller 11, and the motor 12 together with the impeller 11 are disposed in the frame 13. The motor 12 is connected to the impeller 11 and drives the impeller 11 to rotate to generate an air stream for achieving the heat dissipating effect.
In the fan 1, however, the motor 12 is disposed at the center of the impeller 11 and occupies a certain space. So, the areas of the blades of the impeller 11 have to be sacrificed so that the heat dissipating efficiency of the fan 1 is reduced under the integral consideration of the storage space of the motor 12 and the overall size of the fan 1. In addition, the motor 12 itself also generates heat, so the heat dissipating efficiency of the fan 1 is further decreased. Consequently, the design of the fan 1 and the heat dissipating efficiency of the fan 1 are greatly limited.